Download Lab 9.2.7 IP Addressing Basics

Lab 9.2.7 IP Addressing Basics
Objective
•
Name the five different classes of IP addresses
•
Describe the characteristics and use of the different IP address classes
•
Identify the class of an IP address based on the network number
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Determine which part, or octet, of an IP address is the network ID and which part is the host ID
•
Identify valid and invalid IP host addresses based on the rules of IP addressing
•
Define the range of addresses and default subnet mask for each class
Background / Preparation
This lab exercise helps develop an understanding of IP addresses and how TCP/IP networks
operate. It is primarily a written lab exercise. However, it would be worthwhile to review some real
network IP addresses using the command line utilities ipconfig for Windows NT/2000/XP or
winipcfg for Windows 9x/ME. IP addresses are used to uniquely identify individual TCP/IP
networks and hosts, such as computers and printers, on those networks in order for devices to
communicate. Workstations and servers on a TCP/IP network are called hosts and each has a
unique IP address. This address is referred to as its host address. TCP/IP is the most widely used
protocol in the world. The Internet or World Wide Web only uses IP addressing. In order for a host to
access the Internet, it must have an IP address.
In its basic form, the IP address has two parts:
•
A network address
•
A host address
The network portion of the IP address is assigned to a company or organization by the Internet
Network Information Center (InterNIC). Routers use the IP address to move data packets between
networks. IP addresses are 32 bits long according to the current version IPv4 and are divided into 4
octets of 8 bits each. They operate at the network layer (Layer 3) of the Open System
Interconnection (OSI) model, which is the Internet layer of the TCP/IP model. IP addresses are
assigned in the following ways:
•
Statically – manually, by a network administrator
•
Dynamically – automatically, by a Dynamic Host Configuration Protocol (DHCP) server
The IP address of a workstation, or host is a logical address, meaning it can be changed. The Media
Access Control (MAC) address of the workstation is a 48-bit physical address. This address is
burned into the network interface card (NIC) and cannot change unless the NIC is replaced. The
combination of the logical IP address and the physical MAC address helps route packets to their
proper destination.
There are five different classes of IP addresses, and depending on the class, the network and host
part of the address will use a different number of bits. In this lab, different classes of IP addresses
will be worked with and to help become familiar with the characteristics of each. The understanding
of IP addresses is critical to the understanding of TCP/IP and internetworks in general. The following
resources are required:
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CCNA 1: Networking Basics v 3.1 - Lab 9.2.7
Copyright  2003, Cisco Systems, Inc.
•
PC workstation with Windows 9x/NT/2000/XP installed
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Access to the Windows Calculator
Step 1: Review IP address classes and their characteristics
Address classes
There are five classes of IP addresses, A through E. Only the first three classes are used
commercially. A Class A network address is discussed in the table to get started. The first column is
the class of IP address. The second column is the first octet, which must fall within the range shown
for a given class of addresses. The Class A address must start with a number between 1 and 126.
The first bit of a Class A address is always a zero, meaning the High Order Bit (HOB) or the 128 bit
cannot be used. 127 is reserved for loopback testing. The first octet alone defines the network ID for
a Class A network address.
Default subnet mask
The default subnet mask uses all binary ones, decimal 255, to mask the first 8 bits of the Class A
address. The default subnet mask helps routers and hosts determine if the destination host is on this
network or another one. Because there are only 126 Class A networks, the remaining 24 bits, or 3
24
octets, can be used for hosts. Each Class A network can have 2 , or over 16 million hosts. It is
common to subdivide the network into smaller groupings called subnets by using a custom subnet
mask, which is discussed in the next lab.
Network and host address
The network or host portion of the address cannot be all ones or all zeros. As an example, the Class
A address of 118.0.0.5 is a valid IP address. The network portion, or first 8 bits, which are equal to
118, is not all zeros and the host portion, or last 24 bits, is not all zeros or all ones. If the host portion
were all zeros, it would be the network address itself. If the host portion were all ones, it would be a
broadcast for the network address. The value of any octet can never be greater than decimal 255 or
binary 11111111.
st
st
Class
1 Octet
Decimal
Range
1 Octet
High Order
Bits
Network/Host ID
(N=Network,
H=Host)
Default
Subnet Mask
Number of
Networks
A
1 – 126 *
0
N.H.H.H
255.0.0.0
126 (2 – 2)
16,777,214
24
(2 – 2)
B
128 – 191
10
N.N.H.H
255.255.0.0
16,382
14
(2 – 2)
65,534
16
(2 – 2)
C
192 – 223
110
N.N.N.H
255.255.255.0
2,097,150
21
(2 – 2)
254 (2 – 2)
D
224 – 239
1110
Reserved for Multicasting
E
240 – 254
11110
Experimental; used for research
7
Hosts per
Network
(Usable
Addresses)
8
Note: Class A address 127 cannot be used and is reserved for loopback and diagnostic
functions.
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CCNA 1: Networking Basics v 3.1 - Lab 9.2.7
Copyright  2003, Cisco Systems, Inc.
Step 2: Determine basic IP addressing
Use the IP address chart and your knowledge of IP address classes to answer the following
questions:
1. What is the decimal and binary range of the first octet of all possible Class B IP addresses?
Decimal:
From: ________
To: ________
Binary:
From: ________
To: ________
2. Which octet(s) represent the network portion of a Class C IP address? ___________________
3. Which octet(s) represent the host portion of a Class A IP address? ______________________
4. What is the maximum number of useable hosts with a Class C network address? ___________
5. How many Class B networks are there? ___________________
6. How many hosts can each Class B network have? __________________________
7. How many octets are there in an IP address? ________How many bits per octet? __________
Step 3: Determine the host and network portions of the IP address
With the following IP host addresses, indicate the following:
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Class of each address
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Network address or ID
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Host portion
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Broadcast address for this network
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Default subnet mask
The host portion will be all zeros for the network ID. Enter just the octets that make up the host. The
host portion will be all ones for a broadcast. The network portion of the address will be all ones for
the subnet mask. Fill in the following table:
Host IP Address
Address
Class
Network
Address
Host
Address
Network Broadcast
Address
Default Subnet
Mask
216.14.55.137
123.1.1.15
150.127.221.244
194.125.35.199
175.12.239.244
Step 4: Given an IP address of 142.226.0.15 and a subnet mask of 255.255.255.0, answer the
following questions:
What is the binary equivalent of the second octet? _____________________________________
What is the class of the address? _________________________________________________
What is the network address of this IP address? ______________________________________
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CCNA 1: Networking Basics v 3.1 - Lab 9.2.7
Copyright  2003, Cisco Systems, Inc.
Is this a valid IP host address (Y/N)? ______________________________________________
Why or why not?
__________________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
Step 5: Determine which IP host addresses are valid for commercial networks
For the following IP host addresses, determine which are valid for commercial networks and indicate
why or why not. Valid means it could be assigned to any of the following:
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Workstation
•
Server
•
Printer
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Router interface
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Any other compatible device
Fill in the following table:
IP Host Address
Valid Address?
(Yes/No)
Why or Why Not
150.100.255.255
175.100.255.18
195.234.253.0
100.0.0.23
188.258.221.176
127.34.25.189
224.156.217.73
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CCNA 1: Networking Basics v 3.1 - Lab 9.2.7
Copyright  2003, Cisco Systems, Inc.